Genital Embryology Flashcards
Under the control of chromosomal sex, the gondads develop and differentiate, which determines the hormonal environment of the embryo and the development of the internal duct systems and external genitalia. What is the key to sexual dimorphism?
SRY gene
With regards to gonad development, what occurs at week 5? Week 6? At 7 weeks the gonads are undifferentiated and bipotential.
Week 5- transcription factors expressed at genital ridge (WT-1)
Week 6- primordial germ cells migrate from yolk sac to genital ridge
In an XY fetus, what happens at week 7 that leads to testes development?
SRY gene expressed- testes determining factor is produced
With regards to an XY fetus, what hormone is expressed at week 8?
Leydig cells produce testosterone
What stimulates Leydig cells to produce testosterone in the developing fetus?
1st trimester- hCG
2nd/3rd trimester- fetal LH
Once testicular differentiation has been determined, the fetal testes produce two substances critical for male differentiation of these ducts. What are these substances? What cells secrete these substances? What effect do these substances have on sexual differentiation?
Antimüllerian hormone (AMH )- produced Sertoli cells- promotes the regression of Müllerian structures
Testoserone- produced by Leydig cells- stimulates growth of Wolffian duct structures
What is another name for the Mullerian duct? What is another name for the Wolffian duct?
Mullerian duct- paramesonephric duct
Wolffian duct- mesonephric duct
What structures arise from the Mullerian duct?
Fallopian tubes
Uterus
Upper portion of vagina
What structures arise from the Wolffian duct?
Seminal vesicles
Epididymis
Ejaculatory duct
Ductus deferens
Detail the development of internal and external genitalia in a XY fetus without Sertoli cells or lack of Mullerian inhibitory factor.
Develop both male and female internal genitalia.
External genitalia are male.
Detail the development of internal and external genitalia in a XY fetus with 5α-reductase deficiency.
Male internal genitalia.
Ambiguous external genitalia until puberty (increased T cause masculinization)
What structures arise from the genital tubercle?
Glans penis,
Corpus cavernosum and spongiosum
Clitoris
Vestibular bulbs
What structures arise from the urogenital sinus?
Bulbourethral glands
Prostate
Bartholin glands
Skene glands
What structures arise from the urogenital folds?
Ventral shaft of penis
Labia minora
What structures arise from the labioscrotal swelling?
Scrotum
Labia majora
